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I'm having some trouble in my java class at school. We are making a calculator program. I have the display and buttons and everything good. The only thing i need help on is getting the numbers up to the text field after i press the button. We arn't worrying about multiplication, addition or anything yet, so i dont think this will be too hard. The numbers just have to appear up in the text field. This is what i have so far.

Code:

 import java.applet.*;

import java.awt.*;





public class Calculator extends Applet {



  private TextField screen;



  public void init () {

 

    this.setLayout(new GridLayout(3, 1, 3, 3));

    Panel A1 = new Panel();

    this.add(A1);

    Panel A2 = new Panel();

    this.add(A2);

    Panel A3 = new Panel();

    this.add(A3);

    A1.setLayout(new GridLayout(2, 1));

    screen = new TextField(12);

    A1.add(screen);

    Panel B1 = new Panel();

    B1.setLayout(new GridLayout(1, 4, 3, 3));

    B1.add(new Button("C"));

    B1.add(new Button("="));

    B1.add(new Button("/"));

    B1.add(new Button("*"));

    A1.add(B1);

    A2.setLayout(new GridLayout(2, 4, 3, 3));

    A2.add(new Button("7"));

    A2.add(new Button("8"));

    A2.add(new Button("9"));

    A2.add(new Button("C"));

    A2.add(new Button("4"));

    A2.add(new Button("5"));

    A2.add(new Button("6"));

    A2.add(new Button("+"));

    A3.setLayout(new GridLayout(1, 2, 3, 3));

    // 1, 2 and 0

    Panel B2 = new Panel();

    B2.setLayout(new GridLayout(2, 1, 3, 3));

    // 1 and 2

    Panel C1 = new Panel();

    C1.setLayout(new GridLayout(1, 2, 3, 3));

    C1.add(new Button("1"));

    C1.add(new Button("2"));

    B2.add(C1);

    B2.add(new Button("0"));

    // 3, . and =

    Panel B3 = new Panel();

    B3.setLayout(new GridLayout(1, 2, 3, 3));

    // 3 and .

    Panel C2 = new Panel();

    C2.setLayout(new GridLayout(2, 1, 3, 3));

    C2.add(new Button("3"));

    C2.add(new Button("."));

    B3.add(C2);

    B3.add(new Button("="));

    A3.add(B2);

    A3.add(B3);



  }



  public Insets getInsets() {

    return new Insets(5, 5, 5, 5);

  }



}

To start out, you're going to need some sort of EventListener to acknowledge when you have cliked a button. I would set that up next.

Ok, so I rethought the whole thing and this is what I came up with. Anyone see any problems?

Code:

import java.applet.Applet;

import java.awt.*;

import java.awt.event.*;

public class CalculatorSUPER extends Applet implements ActionListener, KeyListener

{

final int MAX_INPUT_LENGTH = 17;

final int INPUT_MODE = 0;

final int RESULT_MODE = 1;

final int ERROR_MODE = 2;

int displayMode;

Label displayLabel;

boolean clearOnNextDigit;

double lastNumber;

char lastOperator;

public CalculatorSUPER()

        {

        super();

        setLayout (new BorderLayout());



        Panel buttonPanel = new Panel();



        Panel numberPanel = new Panel();

        numberPanel.setLayout(new GridLayout(4, 3));        



        addButtonToPanel (numberPanel, new Button("7"), Color.blue);

        addButtonToPanel (numberPanel, new Button("8"), Color.blue);

        addButtonToPanel (numberPanel, new Button("9"), Color.blue);

        addButtonToPanel (numberPanel, new Button("4"), Color.blue);

        addButtonToPanel (numberPanel, new Button("5"), Color.blue);

        addButtonToPanel (numberPanel, new Button("6"), Color.blue);

        addButtonToPanel (numberPanel, new Button("1"), Color.blue);

        addButtonToPanel (numberPanel, new Button("2"), Color.blue);

        addButtonToPanel (numberPanel, new Button("3"), Color.blue);

        addButtonToPanel (numberPanel, new Button("0"), Color.blue);





        buttonPanel.add(numberPanel);







        Panel controlPanel = new Panel();

        controlPanel.setLayout(new GridLayout(4, 1));        





        addButtonToPanel (controlPanel, new Button("C"), Color.cyan);





        buttonPanel.add(controlPanel);



        displayLabel = new Label("");

        displayLabel.setAlignment(Label.CENTER);

        add(displayLabel, "North");







        add(buttonPanel);

        addKeyListener(this);

        requestFocus();



        }

void setDisplayString(String s)

        {

        displayLabel.setText(s);

        }

String getDisplayString ()

        {

        return displayLabel.getText();

        }



void clearLastEntry()

        {

        setDisplayString("");

        clearOnNextDigit = true;

        displayMode = INPUT_MODE;

        }



void addButtonToPanel(Panel panel, Button button, Color backgroundColour)

        {

        panel.add(button);

        button.setBackground(backgroundColour);

        button.addKeyListener(this);

        button.addActionListener(this);

        }

public void actionPerformed (ActionEvent e)

        {

        processButton(e.getActionCommand());        

        }

void processButton(String command) 

        {

        if (command.equals("0")) addDigit(0);

        if (command.equals("1")) addDigit(1);

        if (command.equals("2")) addDigit(2);

        if (command.equals("3")) addDigit(3);

        if (command.equals("4")) addDigit(4);

        if (command.equals("5")) addDigit(5);

        if (command.equals("6")) addDigit(6);

        if (command.equals("7")) addDigit(7);

        if (command.equals("8")) addDigit(8);

        if (command.equals("9")) addDigit(9);



        if (command.equals("C")) clearLastEntry();

        }



void addDigit(int digit)

        {



        if (clearOnNextDigit)

                setDisplayString("");





        String inputString = getDisplayString();

        if ((!inputString.equals("0") || digit > 0)  && inputString.length() < MAX_INPUT_LENGTH)

                {

                setDisplayString(inputString + digit);

                }

        displayMode = INPUT_MODE;

        clearOnNextDigit = false;

        }

        



public void keyPressed(KeyEvent e)

        {

        }

public void keyReleased(KeyEvent e)

        {

        }

        

public void keyTyped(KeyEvent e)

        {

        String command;

        char keyChar = e.getKeyChar();

   if (keyChar == KeyEvent.VK_ESCAPE)

                {

                command = new String("C");

                }

        else

                {

                

                byte bytes[] = {(byte)keyChar};

                command = new String(bytes);

                }

        processButton(command);

        }

}